Time switch device



TIME SWITCH DEvCE Filed July 10i 1933 lm/en'for ANTON/U5 WILHELMUS VINGERHETJ Patented Nov. 6, 1934 UNITED STATES PATENT OFFICE 1,980,146 TIME SWITCH DEVICE Application July 10, 1933, Serial No. 679,810 In Germany July 5, 1932 7 Claims. (Cl. 25o-27) My invention relates to a novel time-Switch device, for the control of the duration of electrically-controlled processes.

In such devices in the past as a rule switches having clock mechanisms were used. Among other drawbacks of such devices, as the requirement of Winding up the springs, and the comparatively high cost, such devices have additional drawbacks which manifest themselves in certain applications, for instance, when used for the control of the duration of X-ray exposures.

In such applications the time of exposure has to be adjustable within certain limits, for instance, for exposure times varying between .1 second to 3 seconds.

While it is of importance that for the lower values, the adjustments can be made in comaratively small steps, for instance, that adjustments for .1, .2 and .3 seconds can be made, 20 on the other hand for the longer time intervals such small steps are undesirable, for instance, after an adjustment of 2 seconds, there is no requirement for the next adjustment to be 2.1 seconds.

The time devices having clock mechanism have a linear character. To provide them with a dial in which the graduation is non-linear, for instance, to provide them with a dial which has a logarithmic scale division, would be highly iml practical.

On the other hand, the blackening of the light-sensitive layers used for taking X-ray exposures varies substantially as a logarithmic function of the time.

Electrical time-switches in which the time interval is determined by the variation of an electric magnitude, which variation may be of a logarithmic function of time, can be obtained, for instance, by using the variation occurring in the conditions of charge of a condenser, whereby the time adjustments are obtained by varying the resistance or capacity of the circuit, or both. In such arrangement, as shown hereinafter, the successive contacts of the switch can be at uniform distance from each other, or if a dial is provided for the switch, the dial can have a uniform scale for a logarithmic variation of the time.

In a specific type of time-switches, especially adapted to control processes of short duration, the duration of the process, for instance, the time of the X-ray exposure, is determined by the time interval required for an electrical magnitude to vary between two fixed values.

As such an electrical magnitude, the charging condition of an electrical condenser has been suggested, which varies according to an exponential function of the time.

In my copending application Ser. No. 679,811 led July l0, 1933 I have described a time-control arrangement which utilizes the charging of a condenser for the control of a three-electrode discharge tube, which tube acts as a time relay. For instance, according to one embodiment of my above invention an alternating voltage is appliedbetween the cathode and anode of the tube and to initiate the process, the duration of which is to be controlled, a positive potential is applied to the grid.

This permits the passage of a discharge through the tube and a current to flow in the anode circuit of the tube during each positive half-cycle of the alternating voltage.

Simultaneously with the application of the positive grid bias, the charging of the condenser through a resistance is started, and by suitable interconnection of the charging circuit of the condenser with the grid of the tube, the grid potential is gradually reduced-according to an exponential function-during the charging of the condenser. After a given time interval the potential of the grid assumes a value which is insufficient to permit ignition of the discharge through the tube. This blocks the current flow in the anode circuit of the tube.

'Ihe anode circuit may comprise a relay switch which electrically controls the process. For instance, in the case of X-ray installations, this relay, upon application of a suiciently positive potential to the grid, closes the primary circuit of the high voltage transformer and when the grid potential has been reduced to a value which is insuicient to ignite the discharge tube, the relay opens this circuit.

The duration of the process can be conveniently varied by making either the resistance or the condenser, or both, variable and by adjusting same to the desired values.

Instead of utilizing the charging of the condenser, its discharge through a variable resistance may be utilized.

In either of the above cases the relay tube, instead of operating as a normally energized relay through which the current is interrupted during the time interval of control, may operate as a normally de-energized relay through which the current only fiows during the control time interval.

One object of my invention is to provide a time Switch device in which the successive contact steps to be passed by the switch member can be spaced apart at equal distances and at the same time the time intervals corresponding to the different contact positions of the switch may vary according to a logarithmic function.

A further object of my invention is to provide for a large number of adjustments without unduly increasing the number of resistance taps or without requiring a large regulating resistance.

A furthervobject of my invention is to use the same regulating resistance in combination with different capacity adjustments.

A still further y object of my invention is to `provide a continuous progressive movement of the switch member to obtain increasing time intervals, whereby when passing from one capacity stage to the following capacity stage the time interval is increased by a step similar, to that between successive resistance stages of a given capacity stage.

A still further object of my invention is'to use a single regulating knob for varying the time interval, whereby for the first capacity stage the switch member successively passes all of the resistance stages and then switches in the second capacity stage and passes again 'all of the resistance stages, etc.

Further objects of my invention will appear as the specication progresses:

According to the invention, both the resistance and the capacity are made variable. The switch is so arranged and interconnected that for a given capacity stage its switching member passes all `of the resistance stages and after having passed same, automatically connects the successive capacity stage for which it again passes all of the resistance stages, etc.

I prefer to so dimension the capacities and resistances that when switching over from the last resistance stage of a given capacity stage to the first resistance stage of the successive capacity stage, the time interval will be increased to the same extent or in the same percentage as it is increased between successive resistance stages of a given capacity stage.

The resistance and capacity stages are computed in known manner, and it'suices here to state that the time interval t required for a voltage difference V, is proportional to the product RC loge V, where R and C are the values of the resistance and capacity included in the circuit.

The product RC is called the time constant of the circuit, and in the present instance determines the time adjustment of the time-switch.

It will appear that with the arrangement of the invention the number of adjustments corresponds to the number of resistance stages times the capacity stages and as the adjustment of the resistance may be made a practically continuous one, a practically continuous graduation of the time interval of the switch may be obtained.

According to a preferred embodiment of the invention the taps of the variable resistance are so selected that the value of the individual resistance stages'form a geometrical series.

Furthermore the ratio between the values of successive capacity st ages is so selected as to correspond to the n-th power of the ratio of two successive resistance values, where n Vis the number of resistance stages. With such arrangement, when switching from the last resistance stage of a given capacity stage to the first resistance or a tapped resistance and also with f one or more contact strips by means of which a plurality of condensers can be successively coni nected in parallel with each other and in series with the resistance, whereby a gradual movement of the switch, for instance its clockwise or counter-clockwise rotation, gradually increases the time constant of the charging or discharge circuit and preferably in steps corresponding'to a geometric progression.

I shall describe my invention with reference to the accompanying drawing, which represents by way of example two embodiments thereof and in which:

Fig. 1 is a circuit diagram showing my novel time-switch in an arrangement in which the voltage variations of a discharging condenser is used for the control of the grid potential of the relay tube.

Fig. 2 is a circuit diagram, showing another embodiment of my invention in an arrangement in which the voltage variations of a charging condenser are used for the control of the grid potential.

The relay or switching tube 2 is a three-electrode tube having an incandescible cathode 14, an anode 30 and a control electrodeA or grid 13.

The discharge tube 2 may be a high vacuum tube, but is preferably a gas-filled arc-discharge device. A transformer winding 1 supplies the voltage for the anode circuit of the tube 2 between its tap 33 and its right end terminal 32. The anode circuit includes the coil of a magnetic switch 8 which is connected between the winding terminal 32 and the anode 30; the cathode 14 connection to the tap 33 completes the anode circuit. For the supply of the heating current the cathode 14 is connected with its other end to the transformer tap 34.

The magnetic switch 8 controls the opening and closure of a contact 7 provided in the control-circuit of the process, the duration of which is to be controlled; for instance in the case of an X-ray installation it is inserted in the primary circuit of the high tension transformer. Normally the contact 7 is kept open by the bias of aV spring 36.

Between the cathode tap 33 and the left terminal 31 of winding 1, there is provided a tap 10 which leads to the pivoting point 35 of the rotatable switch-member 12 of the control switch A. In its illustrated position this member 12 cuts out a smaller or larger portion of a resistance 11, the starting point 40 of which is connected to the grid 13.

As the tap 10 is farther away from the winding terminal 32 (which is connected to the anode 30) than is the cathode tap 34, a potential is impressed upon grid 13, which is negative with respect to cathode 14.

Under such conditions the current iiow through the discharge tube 2 and its anode circuit is blocked irrespective of whether the tube 2 is a gas-lled or a high vacuum tube.

y A condenser 3 is connected with one of its electrodes-as shall appear with its negative electrode-to the tap 10. A charging circuit is provided for this condenser which comprises a rectifier, for instance a gas-,filled rectifier tube ance 38, to theanode 37 of the rectier 4; the

' distance than is the resistance 11.

tap 10, as stated, being connected to the negative electrode of condenser 3 in other arrangements.

The heating current for the cathode 5 of the rectier.4 vmay be supplied from an auxiliary transformer winding 6, although as shown in Fig. 2, a portion of the Winding 1 may serve for this purpose.

The switch '9 is a two-position switch with a wheel 39 and two contact positions I and II. When in position I the condenser 3 is charged through the circuit including the winding portion 31-10, condenser 3, closed switch 9, rectier 4, and resistance 38.

Thus the electrode of the condenser 3, which is connected tothe tap 10, is negatively charged.

The contact point II of the switch 9 is connected to the junction point of the resista/nce terminal 40 and of the grid 13, and when the switch is brought into position II the positive electrode of condenser 3 impresses upon the grid 13 a positive potential. This ignites the tube in the next positive half-cycle of the anode voltage and causes inthe positive half-cycles thereof a current flow through the anode circuit. The magnetic relay 8, which is so constructed as to be responsive to such intermittent current impulses, becomes energized, overcomes thereby the bias of spring 36 and pulls down its armature, thus closing contact 7, and thereby initiating the process.

However, as the condenser 3 gradually discharges over the circuit including the switch 9, contact II, portion of resistance 11, and switchmember 12, the positive bias on grid 13 diminishes until it reaches a value which is insuiiicient to ignite the tube (or in case of a high vacuum discharge tube which is insufficient to permit current flow) in the succeeding positive halfcycles of the anode voltage. The discharge being suppressed, the relay 8 is de-energized, its contact 7 opened, and the process controlled by same is interrupted.

By varying the value of resistance 11 included in the discharge circuit, the time interval at which the grid potential falls to a value which blocks the anode current can be accurately adjusted to the desired value. The greater this resistance portion, the longer will be the time interval. n

'Ihe rotating switch member 12 actually consists of two arms 12' and 12" which extend from the pivot 35 by different lengths. In the case so far described the longer arm 12' was contacting with the taps of resistance 11. To increase the time interval of the switch the member 12 is rotated counter-clockwise. When the entire resistance 11 has been passed by the arm 12' and inserted in the circuit this arm comes into contact with a circular contact segment 15, which is disposed from the pivot 35 at a greater Only the longer arm 12 can contact with this segment, and the shorter arm 12" can only contact with the tap contacts of the resistance 11. The arm 12 contacting with the segment 15 connects a condenser 16 in multiple with the condenser 3. At the same time the shorter arm 12 cuts in a small portion of resistance 11. Upon further counter-clockwise movement of the arm 12, in-

creasing portions of resistance 11 are connected in the circuit.

Thus during the time that the arm 12' contacts with segment 15, the combined capacity of the condensers 3 and 16 are connected in series with the resistance 11 and the time interval of discharge thus further increased. The capacity of condenser 16 is so selected that its inclusion in the circuit provides a uniform variation of theI capacity resistance product when passing froma position in which condenser 3 is connected in series with the total resistance 11 to a position in which the parallel connected condensers 3 and 16 are connected in series with the first tap of resistance 11. V

Fig. 2 shows an arrangement which differs from that of Fig. 1 in several respects. Instead of using the discharge voltage of the condenser to vary the grid bias, the charging voltage of the condenser is used therefor. Furthermore, to vary the time adjustment of the time switch a tapped resistor 23 is connected in series with different capacity values. Further differences will appear thereafter.

The anode circuit of the discharge tube 2 is the same as in Fig. 1.

The potential of grid 13 is normally negatively biased due to the electron emission of the cathode 5 of rectifier tube 4 with which it is electrically connected. Connected to the grid 13 is a wire 50 leading to a junction point 51, to which is connected wire 52 leading to the wheel 53 of a switch arm 22 of a switch A. The arm 22 contacts with one of the twelvecontacts a, b, c, d, a', b', c', d', a, b, c", d", arranged in a circle around the heel 53 of the switch.

The contacts a, a' and a", contacts b, b and b", contacts c, c', and c", and the contacts d, d and d", are groupwise interconnected with each other and are connected by means of wires 54, 55, 56 and 57 to taps 61, 62, 63 and 64 respectively of a resistance 23. The beginning 60 of the resistance 23 is connected to the anode 37 of the rectifier tube 4. Irrespective of which contact the arm 22 contacts with, the grid 13 is interconnected over a lesser or larger portion of resistance 23 with the anode ofv the rectifier tube and due to the electron emission of the cathode 5 obtains a negative bias. The current in the anode circuit of tube 2 being blocked, magnetic relay 8 remains de-energized.

The condenser 3 is connected with one of its electrodes to the junction point 51 and with its other electrode to a junction point 44.

A three-position drum-controller 17 is provided and is shown in the drawing in its development.

Cooperating with the contact segments ofthe` controller are three contactors 41, 42 and 43. The contactor 41 connects with the junction point 51, the contactor 42 with the junction point 44 and the contactor 43 with a tap 20 of the transformer winding 1, which tap lies between the tap 34 and the terminal 32 of the winding 1, close to tap 34. The contact drum has three positions I, II and III and is provided with four contact segments.: a contact segment 18 contacts with contactor 41 in positions II and III; a segment 19, which contacts with contactor 42 in positions I. II and III. and two short segments 21 and 28, which contact with contactor 43 in the positions I and III respectively.

All of the segments 18, 19, 21 and 28 are electrically interconnected.

In the position II of the contact-drum the condenser 3 is short circuited, the circuit going from junction point 51 contactor 41, segments 18 and 19, contactor 42, junction point 44, back to condenser 3. This "is the normal position of the contact-drum when the device is out of use. To charge the condenser 3 the contact-drum 17 is brought into position I in which it closes the charging circuit of condenser 3A as follows: From transformer tap 20, contactor 43, segments 21 and 19, contacter 42, junction point 44, condenser 3, junction point 51, wire 52, switch heel 53 through contact arms 22, one of the contactors a, a', etc. through a lesser or larger portion of the resistance 23, through the rectier tube 4 and winding portion 31-20.

When the charging circuit is closed by moving the contact-drum into position I, the grid 13 obtains a potential sumciently positive to permit the ignition of tube 2. Thus a current can ow through the anode circuit and the relay 8 becomes energized, closes its contact 'I and starts the process.

However, as the condenser 3 becomes gradually charged the potential of the grid 13 is gradually reduced until it again falls below avalue which is suflicient to maintain ignition. Relay 8 is de-energized, contact 7 opened, and the process stopped.

The time interval obtained depends on the position of contact arm 22.

The contacts a, b, c and d, contacts a', b', c and d', and contacts a, b", c" and d" represent three groups of contacts, and it should beV well understood that both the number of contacts per group as well as the number of groups, can be conveniently increased.

Considering the first group of contacts, namely, a, b, c and d, as the arm 22 is moved successively in a clockwise direction to contact with these contacts, increasing portions of the resistance 23 are connected in the charging circuit. The Successive resistance portions or stages are .so selected as to form a geometric series. For instance, if the rst stage falling between points 60 and 61 has a Value r, the second stage falling between points-60 and 62 has'a value kr, the third stage falling between the points 60 and 63 has a value k2r, and the fourth stage falling between the points 60 and 64 has a value cr.

When the switch arm is brought to contact with the next following contact a' the value of the series resistance is reduced to r, but in this position of the switch arm it contacts with a contact segment 24, which parallels the contacts a', b', c', d and a", b", c and d", and which segment is connected with one electrode of a condenser 25 the other electrode of which is connected to junction point 44 and thus to one electrode of' condenser 3. 'I'he heel 53 being connected through junction point 51 with the other electrode of condenser 3, the contacting of arm 22 with segment 24 connects condenser 25 in parallel with condenser 3.

Thus in the position a.' and al1 of the successive contact positions of the switch-arm 22,

the parallel-connected condensers 3 and 25 are and 25, namely C1, Cz be k* times the capacity C1 of condenser 3.

As the time constant for the rst stage was stage k2rC1, for the fourth stage k3rC1, and for madres the fifth stage will be lcrCi, the continuity of the geometric progressionhas been maintained when passing from the fourth to the fifth contact.

'I'he time constants for the contacts b', c', and d', will be k5fC1, kei-C1 and Ic'frCi, respectively. When passing from contact d' to contact a" the resistance is again reduced to the value r; however` at the same time the arm 22 comes into contact with a second contact segment 26 which parallels the last four contacts and which is connected to one electrode of condenser 27, which is thereby connected in parallel with condensers 3 and 25 in the way as has been explained for the parallel connection of the condenser 25. Y

The condenser 27 has such a capacityCa that the combined capacities Ci-i-Ca-i-Ca of condensers, 3, 25 and 27 respectively are equal to Thus the time constant for the position a" is krCl and the time constants for the positions b", c" and d" are k9rC1; A210101; and k11rC1 respectively.

It will thus be seen that the switch provides for twelve different switching times, the time corresponding to successive contacts being a fixed multiple of that corresponding to the preceding contact. Thisis in conformance with the actual requirements in practice as the time required for the blackening of sensitive layers follows a similar progression.

The position III of the contact drum provides forthe prolongation of the duration of the controlledprocess to any desired extent. In this position of the contact drum' both the connections of positions II and I are established. Thus the condenser 3, and alsothe condenser 25 and 27 if they are in parallel therewith, are shortcircuited and at the same time a positive potential is applied to the grid 13. Thus the device may be employed both for fixed short time intervals or for continuous use; when used, for instance, in connection with X-ray installations, the drum is brought into position II for short time exposure, as required in radiographic work, and into position III as required for continuous iluoroscopic work. In such cases I prefer to make the control drum a part of or interconnect it with other regulating means which adjust the voltage and the current of the X-ray installation to the proper requirement of radiographic, respectively fluoroscopic work.

While I have described my invention by reference to specic embodiments thereof and in specic applications I do not wish to be limited to same, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:-

1. A time switch device comprising a discharge tube having an auxiliary electrode and means to vary the potential of said electrode in accordance with a varying condenser charge said means comprising an electric circuit, and means to vary the time constant of said circuit, said latter means comprising a variable resistance and a multi-stage capacity in series arrangement I4 in said circuit, and a switching means for progressively increasing, in successive stages, the resistance from a minimum to a maximum value, said switching means being arranged to connect an increased capacity stage in the circuit after having passed all of the resistance stages at the preceding capacity stage and to pass successively all of the resistance stages at said increased capacity stage.

2. A time switch device comprising an anode, a cathode and a control electrode, a current circuit including said anode and cathode and a second current circuit including a variable resistance and a variable capacity, a portion of said second current circuit being connected between said cathode and said control electrode, means in said second circuit for applying a unidirectional potential to said capacity and thereby applying to the control electrode a potential which, due to the change in charge of the capacity, assumes a value diiering from its initial value, one of said control-electrode potentials rendering the tube conductive, the other rendering it non-conductive, a switch member for regulating said resistance which, when moved from its initial position to its end position, passes at least one position in which it connects an increased capacity stage in said second circuit and before and after reaching said one position increases said variable resistance progressively from a minimum Value to a maximum value, without varying the capacity.

3. A time switch device comprising an anode, a cathode and a control electrode, a current circuit including said anode and cathode and a second current circuit including a variable resistance divided into n stages, the values of the resistances of said stages forming substantially a geometrical series, said second circuit further including a variable capacity, the values of the capacities of successive capacity stages corresponding to the n-th power of the ratio between the resistance values of two successive resistance stages, a portion of said second current circuit being connected between said cathode and said control electrode, means in said second circuit applying a unidirectional potential to said capacity and thereby applying to the control electrode a potential which, due to the change in the charge of the capacity in said second circuit, assumes a value diiering from its initial value, one of said control electrode potentials rendering the tube conductive, the other rendering it non-conductive, a switch member for regulating said resistance, which when moved from its initial position to its end position passes successively said n resistance stages without varying the capacity and then increasing the capacity to the next stage and at the same time reducing the resistance to its rst stage and on continued movement successively passing saidvresistance stages without varying the capacity.

4. In an electric timing device, a discharge tube having an anode, a cathode and at least one control electrode, an anode current circuit including said anode and cathode, a second circuit of which a portion is connected between saidv control electrode and said cathode and means in said second circuit `for establishing a potential difference between the cathode and control electrode varying from one predetermined value to a second predetermined value according to an exponential law, one of said values rendering the tube operative, the other rendering it inoperative, means for varying the time constant of said second circuit, said means comprising a variable resistance and a variable capacity both included in said second circuit and a switch device serving to regulate both said resistance and said capacity to include in the circuit each stage of the capacity with any of the resistance stages successively.

5. In an electric circuit, means for varying the time constant of said circuit, said means comprising a variable resistance having n stages, the values of which form substantially a geometrical series with a ratio lc and a variable capacity having stages the capacity ofwhich have a ratio substantially equal to lc and a switch device to insert each capacity stage in combination with any of the resistance stages successively into the circuit, whereby the time ccnstants of the successive combinations form substantially a geometrical series.

6. An electric timing device comprising a gaslled discharge tube having an anode, a cathode and a control electrode, a source of alternating electromotive force supplying anode current to said tube, a plurality of condensers and a resistance having a plurality of stages, a switch device arranged to connect one of said condensers in series with any of the desired stages of the resistance and in multiple with any desired number of the other condensers, a rectifier and a second switch having two positions, said lastmentioned switch in one position closing a charging circuit from said source of electromotive force to a circuit including the condensers and resistance stage rendered effective by said rst switch device, and said rectifier, and in another position short-circuiting said condensers, the latter being connected to the control electrode which has, when the condensers are discharged, a potential at which the tube is operative and when they are charged to a denite voltage a potential at which the tube is inoperative.

7. A time switch device comprises a discharge tube having a cathode, an anode and a control electrode, a circuit of which a portion is connected between said cathode and said control electrode, means in said circuit for varying the potential of said control electrode to control said discharge tube and means for adjusting the time constant of said circuit, said adjusting means comprising capacity and resistance elements and a progressively movable switching means connected thereto in such a manner that upon movement from its initial position to its end position the resistance in the circuit is varied more than once from one predetermined magnitude to another while the capacity in the circuit is only changed between the periods of resistance variation.

ANTONIUS WILHELMUS VINGERHOETS. 

